1. Field of the Invention
This invention relates to file systems and, more particularly, to performing backups.
2. Description of the Related Art
File systems organize and manage information stored in a computer system. Typically, information is stored in the form of files. File systems may support the organization of user data by providing and tracking organizational structures such as folders and directories. The file system may interpret and access information stored in a variety of storage media, abstracting complexities associated with the tasks of locating, retrieving, and writing data to the storage media.
Backups are typically performed by copying individual files from one physical location to another. In order to locate each file being copied, each file is typically accessed through the file system. The file system maintains metadata (e.g., in an Mode table or master file table) that is used to locate the blocks within each file on the primary storage media. Accessing this metadata may itself involve accessing the primary storage media, and thus locating the files on the primary storage media may involve significant amount of I/O. Additionally, if the file system actually accesses a logical volume that is itself mapped to the primary storage media, generating the block location information from the metadata may involve a significant amount of computation, depending of the complexity of the mapping that relates the logical volume to the physical volume. Furthermore, performing backups through the file system may increase the load on the file system, which may in turn decrease file system performance for actual users for the duration of the backup.
In other systems, backups may be performed without accessing each file through the file system by simply copying the entire storage volume managed by the file system. However, this method of performing backups may unnecessarily reduce network performance by copying needless data in situations where a large portion of the storage volume is not currently in use. As these examples show, improved methods of performing backups are desired.